Pratt & Whitney Canada PT6T

PT6T Twin-Pac T400

PT6T-3B as installed in a Bell 412 helicopter
Type	Turboshaft
National origin	Canada
Manufacturer	Pratt & Whitney Canada
Major applications	AH-1 SeaCobra Bell 212 Bell 412 Sikorsky S-58T
Developed from	Pratt & Whitney Canada PT6

The Pratt & Whitney Canada PT6T Twin-Pac is a turboshaft engine designed for helicopters. Manufactured by Pratt & Whitney Canada, its first application was in the Bell 212 and UH-1N Twin Huey helicopter family. The PT6T Twin-Pac consists of two PT6 power turbines driving a common output reduction gearbox, producing up to 2,000 hp at 6,000 rpm. The engine is designated T400 by the U.S. military.

Development

The U.S. military came very close to not procuring the UH-1N Twin Huey because of the PT6T.^[1] The purchase of the aircraft for U.S. military use was opposed by the Chairman of the House Armed Services Committee at the time, Mendel Rivers. Rivers took this position because the PT6T was produced in Canada. The Canadian government had not supported U.S. involvement in Vietnam, and had opposed U.S. policies in southeast Asia, as well as accepting U.S. draft dodgers. Rivers was also concerned that procurement of the engines would result in a negative trade deficit situation with Canada. Congress only approved the purchase when it was assured that a U.S. source would be found for the PT6T engines. This source was Pratt & Whitney Engine Services in Bridgeport, West Virginia, which was established in 1971 to assemble and test new T400-WV-402 engines. As a result, the U.S. military ordered 294 Bell 212s under the designation UH-1N, with deliveries commencing in 1970.^[1]

Variants

Foreign object damage (FOD) deflection screen on a Bell 412's PT6T

PT6T-3: Basic production model
PT6T-3A: Same as the PT6T-3 but with aluminum (instead of magnesium) gearbox casting, No longer used.
PT6T-3B: Same as the PT6T-3, except for the single power section contingency ratings and has PT6T-6 compressor turbine components.
PT6T-3BE: Same as the PT6T-3B with the removal of the torque sharing function in the torque control and is a PT6T-3BE gearbox fitted with two PT6T-3B power sections.
PT6T-3BF: Similar to the PT6T-3B, except 30-minute one engine inoperative (OEI) rating is equivalent to the 2½ minute OEI rating.
PT6T-3BG: Similar to the PT6T-3BE, except 30 minute OEI rating is equivalent to the 2½ minute OEI rating.
PT6T-3D: Same as the PT6T-3B, except for improved hot section hardware to allow for increased ratings.
PT6T-3DE: Same as the PT6T-3D, except the continuous OEI rating is replaced by a 30 minutes rating.
PT6T-3DF: Same as the PT6T-3DE, except for improved hot section hardware to allow for increased ratings.
PT6T-6: Same as the PT6T-3, except for the 2½ min rating and higher ratings and improved engine parts.
PT6T-6B: Same as the PT6T-6 with the removal of the torque sharing function in the torque control and is a PT6T-6B gearbox with two PT6T-6 power sections.
PT6T-9: Similar to the PT6T-3DF, except for an improved hot section and it is equipped with an engine electronic control system.
T400-C-400: Military PT6T-3
T400-CP-401: Military variant used on the VH-1N variant of the UH-1N.
T400-WV-402: Military PT6T-6, assembled by Pratt & Whitney Engine Services, Inc. in West Virginia

Applications

References

1 2 Drendel, Lou: Huey, pages 14-17. Squadron/Signal Publications, Carrollton, Texas, 1983. ISBN 0-89747-145-8

External links

Wikimedia Commons has media related to Pratt & Whitney Canada PT6.

Pratt & Whitney Canada aircraft engines

Turbojets	J60/JT12

Turbofans	JT15D PW300 PW500 PW600 PW800

Turboprops/Turboshafts	PT6 PT6T PW100 PW200

Auxiliary power units	PW900

See also: Pratt & Whitney aircraft engines

United States military gas turbine aircraft engine designation system

Turbojets	J30 J31 J32 J33 J34 J35 J36 J37 XJ38 J39 J40 XJ41 J42 J43 J44 J45 J46 J47 J48 XJ49 J51 J52 J53 J54 J55 J56 J57 J58 J59 J60 J61 J63 J65 J67 J69 J71 J73 J75 J79 J81 J83 J85 J87 J89 J91 YJ93 J95 J97 J99 J100 YJ101 J102 J400 J401 J402 J403 J700

Turboprops/ Turboshafts	T30 T31 T33 T34 T35 T36 T37 T38 T39 T40 T41 T42 T43 T44 T45 T46 T47 T48 T49 T50 T51 T52 T53 T54 T55 T56 T57 T58 T60 T61 T62 T63 T64 T65 T66 T67 T68 T69 T70 T71 T72 T73 T74 T76 T78 T80 T100 T101 T400 T405 T406 T407 T408 T700 T701 T702 T703 T706 T708 T800

Turbofans	TF30 TF31 TF32 TF33 TF34 TF35 TF37 TF39 TF41 F100 F101 F102 F103 F104 F105 F106 F107 F108 F109 F110 F112 F113 F117 F118 F119 YF120 F121 F122 F124 F125 F126 F127 F128 F129 F135 F136 F137 F138 F400 F401 F402 F404 F405 F408 F412 F414 F415

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